If further studies confirm the findings, doctors might try to identify women most likely to need psychiatric or hormonal treatment after their periods end, the researchers said.

For the study, published online Jan. 6 in the journal JAMA Psychiatry, researchers analyzed the results of 14 studies that included nearly 68,000 older women.

Those whose menopause began when they were 40 and older had a lower risk of depression later in life than those with premature menopause, the study found.

Women who are older when menopause begins and have a longer reproductive life have greater exposure to the hormone estrogen, the study authors said in a journal news release.

The findings suggest "a potentially protective effect of increasing duration of exposure to [natural] estrogens as assessed by age at menopause, as well as by the duration of the reproductive period," wrote Dr. Eleni Th Petridou, of the National and Kapodistrian University of Athens, Greece, and colleagues.

"These findings could have a significant clinical effect by allowing for the identification of a group of women at higher risk for depression who may benefit from psychiatric monitoring or estrogen-based therapies," the researchers concluded.

While the study found an association between early menopause and depression, it did not prove cause-and-effect.

In the United States, the average age of menopause is 51, according to the American College of Obstetricians and Gynecologists.